PLANKTON OF THE GULF OF MAINE 
445 
visible with the naked eye” (Bigelow, 1914a, p. 415). Curiously enough, this species 
has not been detected in our tows over the offshore slope of the bank in summer, 
though represented there in March, 1920 (station 20069). 
The comparative scarcity of Rh. styliformis in the inner parts of the Gulf of 
Maine, contrasted with its abundance over large areas of the open north Atlantic 
in summer (Cleve, 1897; Ostenfeld, 1913), suggests that the optimum salinity for 
8951—28 29 
